We have developed a new device for guiding invasive procedures with ultrasound, which we call the sonic flashlight. We attach a half-silvered mirror and a small flat-panel monitor directly to an ultrasound transducer to project a virtual image of the ultrasound scan into its actual location within the patient. This permits the operator to guide a needle through the skin by aiming directly at the image, using natural handeye coordination rather than looking away from the patient at a conventional display. The device requires no tracking or head-mounted apparatus, and provides an intuitive merger of the visual exterior of the patient with an in situ ultrasound image, which can be simultaneously viewed by others assisting the operator. We believe the sonic flashlight will increase accuracy, safety, and speed, for a wide variety of invasive procedures, and will require less extensive training. We have narrowed our focus to a single application: the placement of the Peripherally Inserted Central Catheter (PICC) line. The PICC line is increasingly viewed as a safe alternative to direct central line placement in the jugular, subclavian, and femoral veins, while being easier to maintain than a peripheral intravenous line. PICC lines can be placed in the upper arm in the Interventional Radiology suite using ultrasound guidance, or at the patient's bedside, where nurses are beginning to use portable ultrasound. However, success rates at the bedside remain relatively low. We believe the sonic flashlight is well suited for improving this success rate. Our specific aims are as follows: (1) Improve the present sonic flashlight to make it ready for clinical use, (2) Test human performance using the sonic flashlight on phantoms and developing in-vitro training procedures, (3) Validate placing PICC lines by interventional radiologists in patients with the sonic flashlight in the Interventional Radiology suite, and (4) Compare success rates between the sonic flashlight and conventional ultrasound for placing PICC lines in patients by IV nurses in an extended study. If successful, at the completion of the proposed three years, the sonic flashlight will have proven beneficial for the insertion of PICC lines in the hands of skilled IV nurses or other non-physicians. Pending FDA approval (for which the data collected in this study will serve), the sonic flashlight will be ready for routine use at the bedside in the hospital, and other settings.